Direction finder



arch 1949 H. G.' BuslGNiEs DIRECTION FINDER Filed sept, 5,` 1945ATmR/VEY Patented Mar. 1, 1949 DIRECTON FINDER Henri G. Busgnies, ForestHills, N. Y., assigner to Federal Telephone and Radio Corporation, NewYork, N. Y., a corporation of Delaware Application September 5, 1945,Serial No. 614,526

6 Claims.. 1

The present invention relates to direction finders and particularly todirection iinders for use on ships.

The antenna system or wave collectors of short wave direction findersare customarily mounted on top of a mast on board ship to reduce theelfect of other masts and the effects of the superstructure.

The types of wave collector or antenna system which reduce polarizationerrors, such as spaced monopoles, spaced loops or spaced dipoles, have.

been found to operate unsatisfactorily under such conditions.

An object of the present invention is the provision of an improveddirection under, particularly for ships.

Another object of the present invention is the provision of a directionfinder for structures such as ships, in which the errors due to masts orto the ships superstructure, are relatively small, and in whichpolarization errors are relatively less than are found in conventionalcrossed-loop direction finders.

Other and further objects of the present invention will become apparentand the invention will be best understood from the following descriptionof an embodiment thereof, reference being had to the drawings, in which:

Fig. 1 is a schematic and block diagram of a direction iinder embodyingmy invention as arranged on a ship; and

Fig. 2 is a detailed perspective View of a portion of the side of theship showing the arrangement of a loop antenna associated therewith.

Referring now to the drawings and in accordance with a feature of myinvention, both sides I and 2 of the metallic hull. of a ship, generallydesignated by the numeral 3, are employed as reiiectors for the wavecollectors or antenna system of a phase comparison direction iinderwhich operates to cover separate sectors l and 5, sector i being coveredby the portion of the antenna systern associated with side i o-f theship 3 While sector 5 is covered by the antenna system associated withside 2. The system of sector operation is generally covered in mycopending application Serial No. 553.598, led September 11, 1944.Sectors li and 5 may be approximately 120 or 130 giving a total coverageof about 240 or 250 of the total 360. On large ships, the ships largesurfaces, oriented toward the front or the back of the ship, could beused to provide two more sectors of her operation especially for thehighest frequencies of the spectrum covered. On small ships, likedestroyers, the dimensions of the sides of the ship are such that goodoperation can be obtained down `to a few megacycles per second and onlarge ships, such as aircraft carriers, battleships, large cruisers,etc., down to one megacycle per second.

Two spaced wave collectors, preferably in the form of loops 6 and i areinstalled on the side I and spaced apart a distance o-f the order of aquarter wavelength. These loops extend substantially at right angles tothe side of the ship. A similar set of loops 8 and Si are installedabout a quarter wavelength apart on side 2 of the ship. All of saidloops are insulated from the hull of the ship and use the hull asreflecting means. The transmission lines Il] from each of said loops maybe brought vertically upward from the loop and directly over the side ofthe vessel or if convenient through an opening in the side. Thetransmission lines may also be used to suspend and support the loops.Each of the loops may be protected by any suitable means such as abubble il of non-metallic material. At the lower frequencies, it ispreferred that the loops be of the type using iron cores.

Because the magnetic field of any incident wave is doubled at thesurface of the metal of the side of the ship. loops are much betteradapted for this purpose than other types of antennas which dependprimarily on the electrical eld. since at the surface of the metal ofthe side of the ship the electrical eld tends toward zero. Loops alsohave the advantage of being much smaller than open antennae. Furthermoreopen antennae cannot be installed at a sufficient distance from the hullto pick up an appreciable signal.

The wave collector system hereinabove described may be used forrelatively low frequencies, such as for example, 1-25 megacycles. Tocover such a range it may be desirable to use two or three sets of loopsspacing them approximately a quarter wavelength apart. While the phasecomparison system may use a transmission line type of phase shifter inmaking the phase comparison, at such frequencies such transmission linephase Shifters become too bulky and other systems are preferablyemployed such as for example, described in my copending applications,Serial No. 481,760, led April 3, 1943, and Serial No. 497,890, filedAugust 9, 1943, now Patent No. 2,444,425, granted July 6, 1948, orpreferably the system hereinafter described which has the advantage ofbeing relatively simple in construction.

Loop is connected by lines iii and over lines i2 directly to one iixedcoil i3 of a goniometer i4. Loop -5 is also connected through a 90 phaseshifter i5 to the other fixed coil It of goniometer iii which is atright angles to coil i3. Loop 'i is likewise directly connected to onecoil l1 of a second goniometer i@ and indirectly connected through a 90phase shifter I9 to the other fixed coil 20 of goniorneter i8. rEherotatable or search coils 2l and 22 of goniometers id and i8respectively, are connected to the primaries 2li and 2li respectively ofa transformer 25 whose secondary 26 is connected through a switch 2l toa direction iinding receiver 28 having at its output an in'- dicator 29,which may be in the form of a cathode ray oscillograph tube. Searchcoils ZI and: 22 are continuously rotated so as to cyclically andoppositely vary the phase of energy derived from the loops 6 and 1 andsuppliedl to transformer 25. That is, search coils 2l and 22 arepositioned and synchronously rotated so that as the phase of the energyderived from one of the loops and 'I is advanced, the phase relationshipof energyN derived from the other of the loop-s is re t'arded. Thesearch` coils are synchronously cont'rolled by any suitable controlmeans 30 which is also used to control the time base of the cathode ray'oscillograph tube 29 to synchronize the sweep thereof with the rotationof the search coils.

A similar phase-shifting system 3i, such as described hereinabove, maybe associated with the loops 3y and 9 on the other side 2 of the shipandv synchronization between this phase-shifting system 35|' and thatheretofore described may be obtained by control means 30. The outputs oithe phase-shifting system 3l and the secondary i@ of" transformer 25 areboth applied to a sector switchv 2T which switches each of theseseparate phase-shifting systems and their respective collectors to thedirection finding receiver as the separate sectors are being scanned.The operation ofthe sector switch 2'! may also be controlled by controlmeans 30, the control means being either electronic or utilizingcommutatore, Selsyn devices, etc., orl combinations of the foregoing, aswill be readily understood by those versed in the art.

Interference with the radiation patterns of the loops 6, 1, 8 and 9 byany energy induced in the lines connecting these loops together or tothe` rest of the direction finding system hereinabove described, isprevented by the sides of the ship which Serve to shield the loops fromthe rest of the apparatus, the rest cf the apparatus being arrangedeither within the hull or some place in the super-structure so that anyeld's produced within said apparatus or lines will not substantiallyaiect the radiation patterns of the loops. The loops are accordinglypreferably arranged a substantial distance below the top of the sides ofthe ship.

In the operation of the direction finder hereinabove described, thephase-shifting system associated with each of the two antennas coveringa given sector is used to continuously and cyclically vary the phaserelationship of the antennas with the direction finding receiver 28. Foreri-- ample' the phase relationships of loops 6 and 'i with respect tothe receiver 2t are continuously and oppositely varied. At the same timethe trace on the cathode ray oscillograph tube 2i? is also' continuouslymoving in a selected. path, such as for example, a circular path. At agiven point during the phase-shifting operation, the voltages appliedfrom loops t and 'i to the direction 'nding receiver 2B will be equaland in phase, the

point or moment at which this occurs depending on the direction fromwhich the signal is being received. At the moment when the voltagesapplied to direction nding receiver 28 are equal and in phase, anindication is produced on the indicator 29, that is, the sweep or traceis deflected. rlhe position of said deflection corresponds to a givendirection from which the energy is being received. After one sector, foreX- ample sector l has been covered by the phase s'iifting operation,then the sector switch operates to connect loops 6 and .fi and sector 5is then covered. This is repeated cyclically.

While I have described the use of two goniorneters in connection witheach sector, by which the phase of energy derived from the two loopscovering each sector is oppositely varied, it is possible to dispensewith one of said goniometers and only vary the phase of energy derivedfrom one of the two loops of the sector while the phase of energyderived from the other loop is not changed. For example, while the phaseof energy derived from loop 5 may be varied by means of the 90 phaseshifter i5 and goniometer lll, loop 7 may be directly connected to theprimary 2f; of transformer thus dispensing with phase shifter l5 andgoniometer lo. However, the system hereinbefore described utilizing agoniometer with each loop for shifting the phase of energy derived fromsaid loop, is a more readily balanced arrangement. It vill also beapparent that while I have described the use of my invention inconnection with a ship, it may also be employed with other structureshaving large metallic surfaces which may serve as reflectors for theloops. Various other changes will occur to those versed in the art.Accordingly, while I have described above the principles of my inventionin connection with specific apparatus, it isto be clearly understood'that this description is made only by way of eX- ample and not as alimitation on the scope of my invention as defined in the accompanyingclaims.

I claim:

1. A direction finder for use with craft having a metallic hullcomprising the combination of a pair of spaced loop antenna unitsmounted in a parallel plane on the outside of said hull adjacent oneside of the craft with said side of the craft serving as a reflectortherefor, a radio goniorneter for each of said antenna units, each ofsaid goniometers comprising a rotor and two stators, means for derivingoutputs of different phase from each of said antenna units, means forapplying each of said outputs to separate stators,

r means for combining the outputs of each of said rotors, a directionnder receiver, an indicator, means for applying said combined outputsthrough said receiver to said indicator, control means for controllingthe rotation of each of said rotors synchronously cyciically andoppositely to vary the phase of energy derived from said goniometers andapplied to said receiver, and means for controlling the operation ofsaid indicator by said control means.

2. An arrangement as. set forth in claim l, wherein said outputs ofdifferent phase comprise means for applying one output of each of saidantenna units to one stator directly, and means for applying anotheroutput of each of said units, through a phase shifter to another of saidstator units.

3. An arrangement as set forth in claim 2, wherein said indicatorcomprises a cathode ray oscillograph and wherein said means to controlthe operation of said indicator comprises means to synchronize the sweepthereof with the rotation of said rotor.

4. An arrangement as set forth in claim 3, wherein said antenna unitsare spaced apart substantially a quarter Wavelength at the systemoperating frequency.

5. A direction finder as set forth in claim 1, further comprising asecond combination of a set of antenna units, radio goniometers, and acontrol means, substantially as described located on the 10 Numberoutside of said hull adjacent another side of the ship, With said lastnamed side of the craft acting as a reector, means for combining theoutputs of the rotors of said second arrangement and means foralternately applying the combined outputs of said first and secondarrangements through said receiver to said indicator.

6. An arrangement as set forth in claim 5, wherein said means foralternately applying the combined outputs comprises one of said controlmeans.

HENRI G. BUSIGN'IES.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

